slightest degree*. We next pierce a hole at each angle of the horn plate, and fix short brass wire pins in each, riveting them firmly by blows of a hammer applied upon the back of the plate. These pins are tapered a little on the face side of the mould.

The mould being thus prepared, we proceed to make a force, or counter-mould. In order to do this, we take several leaves of pasteboard, which we paste together one upon another, and whilst they are still moist, we apply them upon the horn mould in order to receive the impressions of the four pins, and then bore holes through the pasteboards, to correspond therewith, with a pointed instrument. We must employ at first a sufficient thickness of pasteboards so as not to endanger the pins, and add to them successively until the thickness of the force, or counter-mould, when laid underneath the press, shall exceed the length of the pins the eighth of an inch at least.

We then place the whole under the press, and squeeze them carefully, so as not to damage the pins. We also add to the thickness of the pasteboards, if necessary, and when it is become sufficient, we give a strong degree of pressure, and continue to increase it, until we have obtained a perfect impression from the mould in the pasteboards. Sometimes we are obliged to paste small pieces of paper upon the impressed side of the pasteboards, in order to fill the large cavities of the mould, which we could not otherwise accomplish; but every time that we make these additions, we should likewise paste a leaf of paper over the whole surface, in order to retain these additional parts in their places, which otherwise would be liable to become detached.

(To be continued.)

* The Editor has a horn mould in his possession, evidently taken in this manner, from an exquisite medal of Maria Theresa, two inches in diameter, and in which the most delicate markings of the hair, the embroidery, &c. &c. are admirably preserved. He met with this mould at a broker's shop in Somer's Town a few years since; it, no doubt, having been brought over from France by one of the emigrant priests, at the commencement of the Revolution, and was evidently intended to have been employed in embossing straw in the manner described in this article. It however also forms an excellent mould for making casts in plaster of Paris.

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EDWARD CAREY, R. N.*

EVERY one knows that deciduous trees are full of sap during the period, which begins in early spring, and terminates with the complete expansion of the leaves. If at this time a branch be cut off, or if a hole be bored into the trunk, an exsudation of the sap, in a greater or less abundance, will follow. The bark at this time may be stripped off the wood with ease, and in large flakes; and every part of the tree is, so to speak, bathed in moisture. A chemical analysis of sap shows it to be a watery liquor, containing some sugar, mucilage, and extractive matter. In several trees, as the birch and sycamore, the sap is sufficiently copious and saccharine to furnish a fermentable liquor, from which a weak, though perfect wine, may be made; and the sugar-maple of North America produces a sap, from which sugar is annually made in considerable quantity, by boiling it down to a proper consistence. At the fall of the leaf, the wood of a living tree is considerably dryer than it was in spring, and contains a less quantity of sugar, and other easily decomposable vegetable principles.

The old method of preparing oak timber for naval use, appears to have been, to cut down the tree in winter, and after lopping the ends of the branches, to let it remain where it fell till the next summer, without stripping the bark from it. During the spring, the buds in the bark, and those in the sprays which had not been removed, began to vegetate and grow; and in so doing absorbed, consumed, and removed a part, probably nearly the whole, of the sap which was contained in the trunk at the time of its being felled. The imperfect condition of the roads rendered it impossible to convey heavy timber along them, except in the height of summer, so that a tree grown in the weald of Sussex, or even in the remote parts of the

*From Vol. XLVII. of the Transactions of the Society for the Encouragement of Arts, Manufactures, and Commerce.

New Forest, often did not reach Portsmouth Yard till the second year after it had been felled. Here it was stripped of its bark, and stacked either in the open air or under cover, till by continued exposure to a free draught of air, it was seasoned, that is, dried.

During this method of management, fungous rot appears to have scarcely existed in our shipping, whether naval or mercantile.

Of late, within the last fifty years, a great increase has taken place in our navy, without a corresponding supply of oak timber of home growth; and, at the same time, the price of oak bark, for the use of the tanner, has been continually augmenting. These circumstances have led to the practice of felling timber in spring, when, from the abundance of sap, the bark is easiest stripped. But, with the removal of the bark, that vegetation which used to take place during the summer after felling, and which probably was so advantageous in seasoning the wood, is prevented. The naked wood, full of moisture, is exposed to the drying winds of spring and the heat of summer; in consequence of which it becomes shaken and injured by numerous wide clefts, occasioned by partial drying, which admit the rain, and probably also the microscopic seeds of fungi to the heart of the tree. The immense demand of our dock-yards during the last half century of almost incessant war, necessarily occasioned a diminution of the time requisite for seasoning. Hence the timber employed in the construction of shipping has probably of late years been defective, not only from insufficient drying, but also from containing sugar, mucilage, &c. the elements of sap, which, when not acted upon by the living power of vegetation, are susceptible of vinous and acetous fermentation, and, finally, are resolvable into a matter, in which the seeds of fungi will grow with great vigour.

To the duration of timber so circumstanced, its situation in the hull of a ship is singularly unfavourable. The external surface, both without and within the ship, is covered

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with pitch, turpentine, or paint, by which the further escape of moisture (or the process of seasoning), is entirely prevented. The other surfaces of the timber are exposed in darkness to the action of a warm, moist, stagnant air; that is, they are in a situation the most favourable for spontaneous decomposition, the rapidity of which is probably hastened tenfold by the growth of fungi, the slender roots of which penetrating into the pores of the wood, occasion the destruction of its substance to proceed even more rapidly than that of its surface.

It is well known that a saturated solution of common salt is destructive of vegetable life, even in those plants which flourish only in sea water, and a still weaker solution is fatal to all except the maritime plants. Hence it might be argued that ship timber would be secured from rot (as far as this is occasioned by the growth of fungi), by injecting its sap vessels with a solution of salt; and this treatment has been found efficacious in practice. Merchant vessels that convey salt in bulk, are not liable to fungi. A frigate, infested with fungous rot, was accidentally sunk in the Mediterranean, and when weighed again, after remaining under water for some months, was found to be free from fungi, and so continued. In the United States of America, many vessels are built of timber quite green, and in these it is by no means uncommon to fill up the spaces between the timbers with salt, and vessels so salted, it is understood, bear a higher price in the market, on account of their greater durability.

Again, it might be argued, that oil would be efficacious, by penetrating into the sap vessels of timber, and thus preventing the access of moisture: in confirmation of which it may be observed that Greenland ships, and other whalers, are not liable to fungi. Agreeable to this theory, is the practice which prevailed at Boston more than forty-five years ago, to hollow the heads of the timbers, and to fill them with oil, during the building of the ship.

The efficacy of oil, combined with salt, may be argued

from the known fact, that vessels engaged in the Newfoundland fishery, in which the salted fish are stowed in bulk, are not at all liable to fungous rot, and that the bottom of the hull of such vessels will last as long as two or three successive tops.

From these and similar facts, Mr. Carey was convinced that a mixture of oil and salt, applied to the timbers of ships, would be very efficacious in preventing rot. He also thought that it would be found useful to add to this composition a quantity of powdered charcoal, in order to increase its bulk, at small expense, without introducing any noxious ingredient, and which should have the farther advantage of being so light, as in the least possible degree to affect the buoyancy of the vessel.

In the year 1785 he built two schooners, of eighty tons each, in the Island of Cape Breton, for a Mr. Simmons, and filled up all the spaces between the timbers and elsewhere with a composition made of the before mentioned ingredients.

The next year he removed to the Gut of Canso, and there built, of green wood, fresh from the forest, a brig of 200 tons for a Mr. Williams, an American refugee. In this vessel, before he put on the plank sheers, he bored a hole in the centre of each timber-head, fore and aft, on each side, as deep as he could without injuring the treenails, keeping clear of the bolts and nails. These holes he filled. up with a mixture of cod or seal oil, salt, and fine charcoal, brought to as thick a consistence as would run. The spaces between the timbers and elsewhere he filled with a similar composition, but of the consistence of mortar. The way in which it was applied was this: the space being filled with the composition, a block of wood, smaller than the space, was then laid on the surface and driven in ; the compression forced the mixture into the smallest adjacent crevices, and the block was allowed to remain. Stops of wood were also inserted where required, in order to keep the whole in its place, and prevent it from slipping down.

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